\begin{tikzpicture}
    \tkzDefPoints{0/0/O}
    \tkzDefPoint(70:1.5){A}
    \tkzDefPoint(200:1.5){B}
    \tkzDefPoint(340:1.5){C}
    \tkzDefLine[altitude](C,A,B)  \tkzGetPoint{D}
    \tkzInterLC[common=A](A,O)(O,A)  \tkzGetFirstPoint{E}

    \tkzDrawPolygon(A,B,C)
    \tkzDrawCircle[thick](O,A)
    \tkzDrawSegments(A,D  A,E)
    \tkzDrawSegments[dashed](B,E)
    \tkzDrawPoint(O)
    \tkzMarkRightAngle(A,D,C)
    \tkzLabelPoints[right](O)
    \tkzLabelPoints[above](A)
    \tkzLabelPoints[left](B)
    \tkzLabelPoints[right](C)
    \tkzLabelPoints[below](D)
    \tkzLabelPoints[below](E)
\end{tikzpicture}

